1. Field of the Invention
The present invention relates to a method for carrying out bidirectional communications between one first electronic unit and at least one second electronic unit.
2. Description of Related Art
In bidirectional communications between electronic units, an input signal or command signal is normally transmitted from one first electronic unit known as “tool” to at least one second electronic unit which may be referred to as “target.” This input signal is synchronized with an internal clock pulse of the first electronic unit; to recognize a signal level, it should be ensured that the edge of the clock signal is in the middle of the signal, so that the latter may be reliably recognized and read.
The receiving, second electronic unit generates an output signal from the received input signal, which is in turn transmitted to the first electronic unit. The clock signal of the first electronic unit, which is also received, is used in the second electronic unit. However, only the generated output signal is now transmitted back to the first electronic unit, where the received output signal is analyzed using the internal clock pulse.
The problem is that considerable delays, whose magnitude is often unknown, may occur due to the circuit systems provided between the units. These delays, which may also be different for different signals, may be a function of external conditions such as, for example, temperature, and may result in the time shift of the internal clock pulse with respect to the received output signal being such that the output signal may no longer be reliably detected and analyzed.